1. Field of the Invention
The present invention relates to a detergent composition capable of softening fabrics to be washed during a fabric laundering operation.
2. Description of the Prior Art
Detergent compositions for laundering fabrics known in the art usually contain anionic surface-active agents in combination with builders. However, in the case where fabrics, particularly cotton underwear, diapers and the like are washed by using such detergent compositions, the dried fabrics so washed are stiff and do not exhibit a soft finish. In the case of synthetic fiber products, the washed and dried fabrics tend to be statically charged. As is well-known, a static charge on clothes causes an unpleasant feeling when the clothes are put on and taken off, and also, tends to cause the clothes to be dusty.
For the above-mentioned reasons, in order to prevent the static charge on fabrics which are washed by using the above-mentioned type conventional detergent composition and to impart a good feel and drape to the fabrics, fabrics which are washed are generally treated with a fabric softening composition containing, as a main ingredient, a cationic surface-active agent, after the completion of a rinse step in a fabric laundering operation. However, the fabric softening composition cannot be used simultaneously when fabrics are washed by using the above-mentioned conventional detergent composition. This is because not only is a precipitation caused by the interaction of the cationic surface-active agent present in the softening composition with the anionic surface-active agent present in the detergent composition, but also fabric-softening effects, detergency and frothing power are remarkably impaired.
It has been proposed that nonionic surface-active agents, amphoteric surface-active agents or oil components which do not react with the anionic surface-active agents be incorporated into the detergent compositions, so that a good feel and drape is imparted to fabrics during the laundering operation. However, since the above-mentioned additives are poor in adsorption properties with respect to fabrics, the fabric-softening effects are not good, and, even if a large amount of the above-mentioned additives is incorporated into the detergent composition, satisfactory effects can still not be obtained.
A detergent composition containing both an anionic surface-active agent and an cationic surface-active agent in the presence of the specified clay compound has also been proposed (see: U.S. Pat. Nos. 3,862,058 and 3,915,882). A detergent composition in which the reaction of a cationic surface-active agent with an anionic surface-active agent is suppressed by admixing the cationic surface-active agent with a solid organic material slightly soluble in water has been further proposed (see: U.S. Pat. No. 3,936,537). Although these proposed detergent compositions exhibit fabric-softening effects to some extent, they are still not a satisfactory solution for the present requirements in the art.